There are many conventional ways to obtain a customized image on a wall (or other kind of surface): in addition to manual painting, such as fresco or other techniques, wall-papers or films exist with various colours and patterns, Greek frets in wall paper and films, decalcomania transferable products as well as pre-printed decorations, all produced by conventional graphic arts techniques and as such unable to be furnished under specific request, but only selectable among an available pattern inventory. Moreover, the application of such papers exhibits a visual effect far away from the one corresponding to fresco.
If, on the other hand, we look at traditional digital approaches utilizing digital technologies, which appear to be the only way to have exclusive designs on request, the offer today consists in the possibility to print directly on walls by means of a very cumbersome special device so-called “printing plotter” which works vertically (hereinafter such a “printing plotter” will also be simply referred to as a “plotter”).
Normally this technique is used for the decoration of scaffoldings during restorations of churches or other monuments or in advertising signs. Obviously, the use of this device is very difficult and expensive and the printing resolution is rather low (it is only suitable for long distance communications, for example in the advertising boards).
There are also special kinds of wall-papers and wall-films which can be printed by means of a digital device, for example with a water-based ink plotter (scarcely resistant and therefore only suitable for advertising) or with solvent based ink plotters (improved resistance). The result is obviously a paper or a film attached to the wall and, even if beautiful and well camouflaged (there are papers and films with embossed surfaces similar to mural paintings), it remains similar to an adhesive.
Moreover, the mostly advertised product nowadays, and with the best aesthetical results, is a 3M® system, based on a printable film for electrostatic plotter, and used by 3M® customer partners with qualified personal. 3M® partners supply the finished decoration, rather than the printed paper to be applied, since the application technique is very complex. Anyway this is the most interesting possibility, since in some aspects it is the closest one to the approach as proposed by the present invention.
The 3M® system provides for the use of a special paper printable by an electrostatic plotter, or a paper used for the ceramic transfers. In the proposed method this paper must be printed by means of an electrostatic plotter.
The electrostatic plotter is a less common device and more expensive in the management than the ink jet plotter. Moreover this device utilizes inks in a powdery form, similar to toners for laser printers, and so walls will hardly absorb them; anyway, with suitable treatments it is possible to give to the final result an aspect more similar to the fresco than that obtainable with the other above described systems.
This result, however, in addition to the fact that it is not optimum as yet, is obtainable only with a considerable technical and economical stress, since the intervention of qualified personnel is absolutely necessary for the application. This makes an autonomous application by the customer impossible.
Among the existing patent documents relating to decalcomania products, the following have to be mentioned in this description.
Documents U.S. Pat. No. 5,229,201 and U.S. Pat. No. 5,328,535, describe a multilayer decalcomania product including a backing sheet having applied thereon in the quoted order a first water soluble layer, a first coating layer, an image layer including a pigment arranged on said first coating layer, and a second coating layer arranged on the image layer. The second coating layer protects the design during the application on the porous surface. The first water soluble layer can be made of dextrin.
During the application, a bonding agent is firstly applied on the porous surface. Preferably this binder includes a fast acting solvent component such as for instance an alcohol, an ether, an aromatic hydrocarbon or an ester; a moderating agent such as for example a polyhydroxy compound; and a thickening agent, such as a polyvinyl alcohol or cellulose. In the next step, the backing layer is removed by applying water to said decalcomania product and then this is applied without the backing layer to the connective agent layer, directly on the side of the first coating layer.
It can be observed that the application of such a decalcomania product requires a surface pre-treatment.
Document U.S. Pat. No. 3,510,385 describes a decalcomania product such that, after its application, the image can be modified on the substrate surface by means of an in situ treatment.
The decalcomania product is made up of a backing layer and several transferable layers. The upper layer is an adhesive layer (preferably a pressure-sensitive adhesive layer) and is not soluble or dispersable in water, while the inner layer, on the contrary, due to its composition, is soluble or dispersable in an aqueous medium. It is important that in the decalcomania product's composition there is at least one layer on which the aqueous medium cannot have any effect. In the case of two layers, the one placed directly on the support is a water soluble layer and the following one is a non water soluble and adhesive layer (preferably a pressure sensitive adhesive layer). The pigment is arranged in some areas of the soluble layer, so that, after the application of the decalcomania product on the substrate, the soluble layer or a portion thereof may be removed by water, making the pigment appear. In the case of a multi-layer version, it is possible to repeat this step several times, so as to obtain every time a different image on the substrate.
It is clear that this decalcomania product cannot be printed by the final user, but it is to be decorated before applying the last functional layer, namely the adhesive one, whereby it is to be considered among those decalcomania products that restrict the selection of the image to the ones furnished by the manufacturer.
Document WO 97/42040 describes a decalcomania product made up of several layers, these are in order: a water permeable support with a release layer formed of a water releasable adhesive on its surface, eventually a barrier layer and an image layer printable by means of ink jet printer. In a particular application, the support is peeled away after the transfer has been applied to walls, the image layer after having coated it with a binding agent, as in the case of the preceding document.
Anyway it is not possible to produce the transfer following the instructions described in the document, so this simply remains a description of a good idea.
Document U.S. Pat. No. 3,533,822 describes a transfer particularly for ceramic surfaces, made up of a support on which layers are placed as follows: a release layer, an optional barrier layer, a pattern or image layer and an adhesive layer. After the application of the transfer on a surface, the support is removed by dampening it with water. In the document we can find the composition of the release layer, which is made of at least an ester of polyethylene glycol selected from polyethylene glycol monolaurates, polyethylene glycol stearates, polyethylene glycol oleates. The one described in this last document is a common transfer and needs an adhesive layer on the image layer.
Document JP2004004212 introduces a product built of a pad layer and a transfer layer, laminated subsequently on the surface of a base material. A release layer is placed on the back side of the base material.
The transfer layer is a coating obtained by spreading a mixture of polyvinyl alcohol, an hydrorepellent resins and a solvent on the base material, and it has a superficial roughness of 1-20 μm. The pad layer includes a soft polymeric resin having shock absorbing properties. The transfer layer can be printed with an electro-photographic device and can transfer the image to a target transfer substrate. The advantage of this kind of transfer is that it is possible to repeatedly print faint images by toner to target transfer substrate. In the preferred embodiment, a soaking layer containing a polymeric resin adapted to prevent the base material from absorbing water is interposed between the pad layer and base material, it is aimed at maintaining the smoothness transfer layer as a result of the strength of the interlayer bond. The preferred polymeric resins contained in the pad layer is a urethane resin having an elasticity figure of 500-1500%, as measurable with JIS K 7127. The release layer is made of a silicone resin. The preferred solvent is a butyl-cellosolve.
This decalcomania product needs a pad layer and a further layer arranged on the back of the support base material.
Document EP 1457513 describes a mixture, which can be also used to obtain a decalcomania product, comprising one or more isostatic modified polypropylenes (MPP) or a polypropylene-a-olefin copolymer, and one or more polymers or resins, wherein said MPP or MPP copolymer is modified with one or more carboxy, anhydride, hydroxy or epoxy groups.
Document GB793,391 discloses a decalcomania or transfer material of the type comprising a water-permeable backing, such as porous water-leaf paper, an adhesive layer, and a sizing layer intermediate the backing and adhesive. A lacquer coating may be applied over the adhesive coating or the printing may be applied directly to the adhesive coating. To transfer the print the paper is soaked in water until the adhesive coating is softened sufficiently to permit the print to be slipped off, after which the print is mounted on the article to be decorated. At least part of the adhesive layer is transferred with the separable layer to stick the transfer to the surface to which it is to be applied.
The sizing layer is provided to resist to curling during printing and applying the decalcomania.
The adhesive layer comprises a bottom gumming and a top gumming layers. Top gumming, which is the printable layer, is preferably made of dextrin, which may be mixed with animal glue, resin dispersions, wetting agent and a plasticiser such as glycerine and sorbitol.
Finally, document EP 1498285 discloses a decalcomania product which consists of a water-permeable and water soaking resistant support, preferably a paper or a fabric sheet with short fibers, which is covered by a first layer or “coat” of a water resistant material at room temperature, made of one or more substances of mineral, animal or vegetable origin and preferably selected from the group comprising gelatins, alginates, starches, dextrin, methylcellulose, ethylcellulose, carboxymethylcellulose, urea resins, phenolic resins, arabic gum and tragacanth gum, a second layer spread on the first layer, made of one or more transparent synthetic and water-permeable resins, which are water or other solvent soluble and are preferably selected from the group comprising vinyl, acrylic, epoxy and polyurethane resins, a waterproof decoration being printed on said second layer which has to be transferred onto a generic surface. The decoration can be printed by exploiting the common technologies, such as offset, rotogravure, serigraphy, flexography, typography print or by computerized print by means of printer or plotter. The support, the coat and the synthetic resin are bonded to one another without any inter-penetration, and the decalcomania product can be micro-punctured before or after printing the decoration onto the second layer.
In this decalcomania product, the first layer or “coat” on the support is water resistant at room temperature, water being needed for releasing the support member after application. This means that the decalcomania product needs a water soluble, synthetic adhesive resin layer to be spread on the surface to be decorated.
Some of the transferable products as described in the above cited documents have the same above mentioned problems, namely the need of a pre-treatment of the application surface or the need a special additional layers, all of which make the manufacturing expensive, and in addition they turn out to be technically impossible to realise and complex, and expensive to be manufactured and/or applied.